Device for producing haptic feedback

ABSTRACT

In an embodiment a device includes at least one piezoelectric actuator including a plurality of piezoelectric layers and a first reinforcing element and a second reinforcing element, wherein the piezoelectric actuator is arranged between the reinforcing elements, wherein the piezoelectric actuator is configured to alter its expansion in a first direction when an electrical voltage is applied, and wherein the reinforcing elements are configured to deform on account of a change in an expansion of the piezoelectric actuator such that a central region of the respective reinforcing element is moved relative to the piezoelectric actuator in a second direction, the second direction being perpendicular to the first direction.

This patent application is a national phase filing under section 371 ofPCT/EP2017/069708, filed Aug. 3, 2017, which claims the priority ofGerman patent application 102016116763.0, filed Sep. 7, 2016, each ofwhich is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The invention relates to a device for producing haptic feedback. Theinvention further relates to an electronic apparatus comprising thedevice for producing haptic feedback. The invention furthermore relatesto the use of the device as a drive for haptic feedback.

BACKGROUND

In touch-sensitive screens, artificially produced haptic feedback isdesired when a virtual key is pressed, in order to improve theoperability. This is of importance in the automotive field, inparticular, since a user cannot permanently look at the screen. Thehaptic feedback can be used, for example, to communicate to the user thefact that settings carried out by the user are successfully implemented.

However, existing devices for producing haptic feedback are usually verycomplex and have an inefficient transmission.

SUMMARY OF THE INVENTION

Embodiments provide an improved device for producing haptic feedback,for example, a device which is particularly simple, space-saving and/orcost-effective.

According to an embodiment, a device for producing haptic feedback isspecified. The device serves as a drive for haptic feedback. The deviceis configured to produce haptic feedback for electronic apparatuses, forexample, for touch-sensitive screens. By way of example, the device isintended to be configured to bring about an offset of the screenparallel to a screen surface.

In a simplified representation, screen and device (drive) correspond toan oscillatory mass-spring system. In this case, the resonant frequencyf_(o) (frequency of the free oscillation without excitation) results as:f_(o)=½π·√(D/m). D is the stiffness of the drive or of the device. m isthe mass of the screen. m is generally between 300 g and 400 g.

The device has a specific minimum stiffness D so that the desired offsetof the screen can be achieved. f_(o) must be greater than the reciprocalof the excursion duration T, otherwise the screen does not move or onlypartly moves concomitantly. An offset is intended generally to have aduration of between 7 ms and 10 ms. It thus holds true that: D≥m(2π/T)². Given T=7 ms and m=400 g this results in a minimum stiffness of0.32 N/μm for the device (drive). The stiffness is influenced, forexample, by a geometry and/or a material and/or a thickness or verticalextent of the device or the components thereof.

The device comprises at least one piezoelectric actuator. The actuatorcomprises a multiplicity of piezoelectric layers. Internal electrodesare arranged between the piezoelectric layers. Piezoelectric layers andinternal electrodes are arranged one above another to form a stack. Thestack height is preferably less than or equal to 3 mm.

The device furthermore comprises a first reinforcing element. The devicecomprises a second reinforcing element. The piezoelectric actuator isarranged between the reinforcing elements. The reinforcing elementsserve for increasing the stiffness of the device. The reinforcingelements furthermore serve for stroke amplification.

The reinforcing elements are arranged in a stacking direction of thepiezoelectric layers at least partly on a top side and an underside ofthe actuator. The device is formed symmetrically about a horizontal axisor longitudinal axis of the device.

The piezoelectric actuator is configured and arranged to alter itsexpansion in a first direction when an electrical voltage is applied.Preferably, when an electrical voltage is applied, the expansion of thepiezoelectric actuator takes place transversely with respect to thepolarization direction of the piezoelectric layers and with respect tothe electric field (d31 effect). Preferably, when an electrical voltageis applied, the expansion takes place transversely with respect to thestacking direction of the piezoelectric layers.

The respective reinforcing element is formed in integral fashion.Preferably, the respective reinforcing element has a partial region. Thereinforcing elements are configured and arranged to deform on account ofthe change in the expansion of the piezoelectric actuator in such a waythat the partial region of the respective reinforcing element is movedrelative to the piezoelectric actuator in a second direction. The seconddirection is perpendicular to the first direction. The second directionpreferably extends along the stacking direction of the piezoelectriclayers.

As mentioned above, the stroke of the actuator is amplified by thereinforcing elements. An effective drive for producing haptic feedbacksis thus made available. By virtue of the small stack height, as aseparating process it is possible to use “cutting” instead of “sawing”.Furthermore, the contacting of the actuator is simplified. Both lowerthe production complexity and hence the costs. Furthermore, only a smallspace requirement is needed on account of the small height. Overall adevice is provided which not only provides the required deflection forproducing haptic feedback but is also simple, cost-effective andcompact.

In accordance with one exemplary embodiment, the reinforcing elementseach have at least one end region. Preferably, each reinforcing elementhas two end regions. The respective reinforcing element is preferablyformed in rectangular or strip-shaped fashion. The respectivereinforcing element has a length and a width. The length is greater thanthe width of the reinforcing element by a multiple. By way of example,the length is 5 times, 10 times, 12 times or 15 times the width. By wayof example, the width of the respective reinforcing element is between 3mm and 10 mm. By way of example, the length of the respectivereinforcing element is between 50 mm and 100 mm.

The end regions are situated respectively in the region of the end facesof the reinforcing element. The respective end region is directlyadjacent to the respective partial region. In particular, the respectivepartial region transitions into an end region toward both (end)sides.The partial region thus constitutes a central region of the reinforcingelement.

The end region is configured and arranged in such a way that upon achange in the expansion of the piezoelectric actuator, a movement of theend region in the second direction does not occur. A relative movementbetween the respective end region and the partial region of thereinforcing element thus occurs. The haptic feedback is produced by therelative movement of the respective end region with respect to therespective partial region. A simple and effective device is thusprovided.

Preferably, the end region is in each case directly at the piezoelectricactuator. Preferably, the end regions of the first reinforcing elementbear on a top side, at least on partial regions of the top side, of theactuator, Preferably, the end regions of the second reinforcing elementbear on an underside, at least on partial regions of the underside, ofthe actuator.

Preferably, the respective end region and the piezoelectric actuator areconnected to one another by an adhesive connection. A simple,cost-effective and effective connection between reinforcing element andactuator is thus achieved. The necessary stiffness of the device isensured. Moreover, the geometry of the reinforcing elements issimplified as a result. Complicated geometries for forming a clampingconnection between reinforcing element and actuator can be dispensedwith, in particular.

Preferably, the respective reinforcing element comprises a metal strip.The metal strip is preferably rolled. The respective reinforcing elementcan comprise a sheet-metal strip. The respective reinforcing element ispreferably formed in flat fashion, that is to say has only a smallmaximum thickness. The maximum thickness or vertical extent of thereinforcing element is preferably less than or equal to 1.0 mm. Aparticularly space-saving device is thus achieved.

The respective reinforcing element is embodied as curved or bent. Inparticular, the reinforcing element has regions or sections which do notextend along a plane, but rather form an angle with respect to alongitudinal axis of the reinforcing element (oblique sections). Bycontrast, other regions or sections extend parallel to the longitudinalaxis. Parallel and oblique sections merge directly or straight into oneanother. The specific shaping of the reinforcing elements serves toensure the required stiffness of the device.

In accordance with one exemplary embodiment, the respective partialregion is arranged at a distance from a surface of the piezoelectricactuator. In particular, there is a free space situated between thepartial region and a top side and/or an underside of the actuator. Themovement of the partial region in the second direction is made possibleas a result. A maximum height or vertical extent of the free spaceamounts, for example, to less than or equal to 2.5 mm, for example, 1.2mm. Accordingly, the device itself has a thickness of less than or equalto 10 mm. A compact and space-saving device can be made available as aresult.

In accordance with one exemplary embodiment, the respective reinforcingelement has at least one thinned portion, preferably a plurality ofthinned portions. By virtue of the thinned portion, the thickness of thereinforcing element is reduced pointwise. The thinned portion has adepth or vertical extent of less than or equal to 0.8 mm, for example,0.75 mm. The respective reinforcing element bends at the location of thethinned portion upon the movement in the second direction. A simple andstable reinforcing element is achieved as a result. The transmissionbecomes movable for the actuator and stiff for the load (screen) as aresult of the thinned portion. The efficiency of the transmission isincreased as a result.

In accordance with one exemplary embodiment, the thinned portion has anindentation in a surface of the respective reinforcing element. By wayof example, the thinned portion comprises a notch. The thinned portioncan be formed at a top side and/or an underside of the respectivereinforcing element. The thinned portion can be stamped or milled into asurface of the reinforcing element. The thinned portion can have a roundor angular profile.

In accordance with one exemplary embodiment, a thinned portion is formedin a transition region between the partial region and the end region ofthe respective reinforcing element. As a result, the reinforcing elementcan bend in the transition region. A loading of the connection betweenthe end region of the reinforcing element and the actuator can thus bereduced.

In accordance with one exemplary embodiment, the respective partialregion has a central region. The respective partial region furthermorehas at least one connection region, preferably two connection regions.The connection regions are adjacent to the central region from two sides(end sides). The connection regions connect the central region of therespective partial region to the two end regions.

The central region extends parallel to a surface of the piezoelectricactuator. The connection region extends obliquely with respect to thesurface of the piezoelectric actuator. A thinned portion is formed in atransition region between the central region and the connection region.By virtue of the thinned portion, the reinforcing element can bend inthe transition region.

In accordance with a further aspect, an electronic apparatus isspecified. The electronic apparatus comprises a device for producinghaptic feedback. The device corresponds in particular to the devicedescribed above. All features that have been described in associationwith the device are also applied hereinafter to the electronicapparatus.

The device constitutes a drive for haptic feedback. The electronicapparatus comprises a first mechanical element, for example, atouch-sensitive screen. The electronic apparatus comprises a secondmechanical element, for example, a weight or a housing element. Thefirst reinforcing element is secured to the first mechanical element andthe second reinforcing element is secured to the second mechanicalelement, or vice versa. In particular, the reinforcing elements aresecured to the mechanical elements in such a way that upon a deformationof the piezoelectric actuator, the mechanical elements are movedrelative to one another. Consequently, an offset of the screen parallelto the screen surface and hence haptic feedback for the user are broughtabout. A particularly user-friendly electrical apparatus is thusachieved.

In accordance with a further aspect, the use of a device is described.In particular, the use of the device described above is specified. Allfeatures that have been described in association with the device arealso applied to the use. In particular, the device is used as a drivefor haptic feedback in touch-sensitive screens in the automotive field.A simple, cost-effective, space-saving and efficient drive which can beused to produce haptic feedback for the user is made available by thedevice.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in greater detail below on the basis ofexemplary embodiments and with reference to the associated figures.

The drawings described below should not be interpreted as true to scale.Rather, individual dimensions may be illustrated as enlarged, reduced oreven distorted for the sake of better illustration.

Elements which are identical to one another or which perform the samefunction are designated by identical reference signs.

FIG. 1 shows a device for producing haptic feedback in accordance withthe prior art;

FIG. 2 shows a sectional view of a device for producing haptic feedback;

FIG. 3 shows a perspective view of a partial region of the device inaccordance with FIG. 2;

FIG. 4 shows a perspective view of the device in accordance with FIG. 2;

FIG. 5 shows a perspective view of a device for producing hapticfeedback in accordance with a further exemplary embodiment; and

FIG. 6 shows a device integrated as a drive for haptic feedback into anelectronic apparatus according to an embodiment.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

FIG. 1 shows a device for producing haptic feedback in accordance withthe prior art. The device comprises a piezoelectric actuator 1comprising a multiplicity of piezoelectric layers 1 a and internalelectrodes arranged therebetween. The piezoelectric layers 1 a arestacked in the longitudinal direction. A respective metallization 2 isformed at opposite outer surfaces of the actuator 1. The actuator 1 isarranged in a metal housing 3, for example, which serves for strokeamplification.

The device known according to the prior art exploits the longitudinalpiezoelectric effect (d33 effect). In longitudinal actuators, theelectric field is applied in the ceramic layer parallel to the directionof polarization. This induces an extension or deflection in thedirection of polarization. In this case, individual piezoelectric layers1 a yield relatively small deflections. In order to achieve technicallyusable deflection values, stacked actuators are used, therefore, inwhich a multiplicity of piezoelectric layers 1 a are interconnectedmechanically in series and electrically in parallel.

Consequently, the piezoelectric actuator 1 is very complex andmanufactured with large dimensions, as a result of which the devicebecomes voluminous and expensive. Furthermore, the piezoelectric layers1 a of the actuator 1 have a very stiff and inefficient transmission.

In contrast thereto, FIGS. 2 to 5 show a device 10 according toembodiments of the invention for producing haptic feedback, whicheliminates the disadvantages mentioned above. FIGS. 2 to 4 will firstlybe considered in detail below.

The device 10 comprises a piezoelectric actuator 11. The piezoelectricactuator 11 constitutes a sintered component having a multiplicity ofpiezoelectric layers 22 and internal electrodes 21. The piezoelectricactuator 11 comprises in particular a multiplicity of piezoelectric oractive layers 22 arranged one above another to form a stack. By way ofexample, the piezoelectric actuator 11 can comprise up to 100piezoelectric layers 22, e.g., 70 piezoelectric layers 22. The internalelectrodes 21 are arranged between the piezoelectric layers 22 (FIG. 2).In this case, internal electrodes 21 of different polarities arearranged alternately.

The piezoelectric layers 22 can be lead zirconate titanate ceramics (PZTceramics). The PZT ceramic can furthermore additionally contain Nd andNi. Alternatively, the PZT ceramic can furthermore additionally compriseNd, K and, if appropriate, Cu. Alternatively, the piezoelectric layerscan have a composition containing Pb(Zr_(x)Ti_(1-x))O₃+yPb(Mn_(1/3)Nb_(2/3))O₃.

The piezoelectric layers 22 have a stacking direction S (FIG. 2). Thestacking direction S extends along end or side faces 24 of the actuator11. In particular, the piezoelectric layers 22 are stacked along avertical extent or thickness of the actuator 11.

The actuator 11 has a width or first horizontal extent of less than orequal to 10 mm, for example, 5 mm. The actuator 11 has a length orsecond horizontal extent of less than or equal to 100 mm, for example,60 mm. The actuator 11 can have, for example, a basic area of 5 mm×60 mm(width×length). The actuator 11 preferably has a vertical extent orthickness that is less than or equal to 3 mm. By way of example, therespective piezoelectric layer 22 has a thickness of less than or equalto 40 μm, for example, 39 m.

The actuator 11 has two insulation regions 12 (see FIG. 3). Therespective insulation region 12 is formed in an end region of theactuator 11. In particular, the respective insulation region 12 isformed in the region of an end face 24 of the actuator 11. Therespective insulation region 12 has a length of less than or equal to 2mm.

In the insulation region 12 only internal electrodes 21 of one polarityextend as far as the end face 24 of the actuator 11. The insulationregion 12 can be used for contacting the actuator 11. By way of example,the respective insulation region 12 can be provided with externalelectrodes 23 for electrical contacting (FIG. 2).

The actuator 11 is configured such that when an electrical voltage isapplied, a deformation of the actuator 1 takes place (expansion indirection R1, see FIGS. 2 and 3). In particular, the piezoelectriclayers 22 are polarized in such a way that applying an electricalvoltage between the internal electrodes 21 leads to a transversecontraction of the actuator 11, in the case of which the length of theactuator 11 changes perpendicular to the stacking direction S. Anexpansion of the actuator 1 thus takes place transversely with respectto the polarization direction and with respect to the electric field(d31 effect).

In order to further reinforce the effect of the change in length in thestacking direction S, the device comprises two reinforcing elements 13a, 13 b. If voltage is applied to the actuator 11, then the reinforcingelements 13 a, 13 b deform at least partly on account of the change inthe expansion of the actuator 11, as will be described in detail later.

The actuator 11 is arranged between the reinforcing elements 13 a, 13 b.The reinforcing elements 13 a, 13 b bear at least partly on a top side25 and respectively an underside 26 of the actuator 11. The respectivereinforcing element 13 a, 13 b preferably has a width that correspondsto the width of the actuator 11. The same preferably applies to thelength of the reinforcing elements 13 a, 13 b. Preferably, therespective reinforcing element 13 a, 13 b has a basic area of 5 mm×60 mm(width×length).

The respective reinforcing element 13 a, 13 b is formed in integralfashion. The respective reinforcing element 13 a, 13 b has a rectangularshape. The respective reinforcing element 13 a, 13 b is formed instrip-shaped fashion. The respective reinforcing element 13 a, 13 b isformed in curved or bent fashion. By way of example, the respectivereinforcing element comprises a sheet-metal strip. The sheet-metal stripis bent, as explained in detail below.

Each of the integral reinforcing elements 13 a, 13 b is subdivided intoa plurality of regions or sections. In this regard, the respectivereinforcing element 13 a, 13 b has a partial region or first region 17a, 17 b. The partial region 17 a, 17 b respectively has a first sectionor central region 19 a, 19 b (FIG. 4). The central region 19 a, 19 b hasa length of less than or equal to 4 mm, preferably 3 mm.

The partial region 17 a, 17 b furthermore respectively has two secondsections or connection regions 20 a, 20 b (FIGS. 2 and 4). The twoconnection regions 20 a, 20 b of the respective reinforcing element 13a, 13 b are directly adjacent to the central region 19 a, 19 b of therespective reinforcing element 13 a, 13 b. In other words, the centralregion 19 a, 19 b of the respective reinforcing element 13 a, 13 b issurrounded by the two connection regions 20 a, 20 b toward both sides.

The respective reinforcing element 13 a, 13 b furthermore has two endregions 18 a, 18 b. The respective end region 18 a, 18 b preferably hasa length of less than or equal to 5 mm, for example, 4.5 mm. The endregions 18 a, 18 b are directly adjacent to the connection regions 20 a,20 b of the respective reinforcing element 13 a, 13 b. In other words, arespective connection region 20 a, 20 b connects an end region 18 a, 18b to the central region 19 a, 19 b of a reinforcing element 13 a, 13 b.

The two end regions 18 a, 18 b of the respective reinforcing elementbear directly on a surface of the actuator 11. In this regard, the firstand second end regions 18 a of the first reinforcing element 13 a bearon a partial region of the top side 25 of the actuator 11. Furthermore,the first and second end regions 18 b of the second reinforcing element13 b bear on a partial region of the underside 26 of the actuator 11.

The end regions 18 a, 18 b are preferably connected to the surface ofthe actuator 11 in a non-releasable manner. In particular, the endregions 18 a, 18 b are connected to the surface of the actuator 11 bymeans of an adhesive-bonding connection. An underside of the respectiveend region 18 a, 18 b together with a partial region of the top side 25and respectively underside 26 of the actuator 11 form anadhesive-bonding surface 15 (FIGS. 3 and 4). Adhesive material isapplied on the adhesive-bonding surface 15 and the reinforcing elements13 a, 13 b are connected to the actuator 11 in this way. By using anadhesive-bonding connection instead of a clamping connection, forexample, it is possible for the geometry of the reinforcing elements 13a, 13 b to be kept very simple.

The respective partial region 17 a, 17 b is at a distance from thesurface of the actuator 11. In particular, a free region 16 (FIGS. 2 and3) is situated between the respective partial region 17 a, 17 b and theunderside 26 and respectively the top side 25 of the actuator 11. Thefree region 16 has a height h (FIG. 3). The maximum height h and thusthe maximum distance between the actuator 11 and the partial region 17a, 17 b is preferably less than or equal to 3 mm, preferably 2.5 mm.This results in a maximum total thickness of the device 10 of preferably10 mm.

The height h of the free region 16 varies along the respective partialregion 17 a, 17 b. In this regard, the central region 19 a, 19 b of therespective partial region 17 a, 17 b is configured such that it extendsparallel to the surface of the actuator 11. The height h of the freeregion 16 is thus maximal in the region of the central region 19 a, 19b. By contrast, the respective connection region 20 a, 20 b extendsobliquely with respect to the surface of the actuator 11. In otherwords, the respective connection region 20 a, 20 b forms an angle withthe top side 25 and respectively the underside 26 of the actuator 11.The angle is preferably less than or equal to 45°. The height h of thefree region 16 thus decreases in the direction from the central region19 a, 19 b toward the end region 18 a, 18 b of the respectivereinforcing element 13 a, 13 b. Consequently, the respective reinforcingelement 13 a, 13 b has a bent shape.

The respective reinforcing element 13 a, 13 b furthermore has at leastone thinned portion 14, preferably a plurality of thinned portions 14.In FIGS. 2 to 5, the respective reinforcing element 13 a, 13 b has fourthinned portions 14. In this case, the thinned portions 14 can beregarded as a region in which the respective reinforcing element 13 a,13 b is thinner, that is to say has a smaller vertical extent orthickness than in the remaining region. A thinned portion 14 preferablyhas a depth or vertical extent of less than or equal to 0.8 mm,preferably 0.75 mm. The maximum thickness of the respective reinforcingelement 13 a, 13 b is preferably 1 mm. At the location of a thinnedportion 14, the respective reinforcing element 13 a, 13 b thus has aresidual thickness of 0.25 mm.

The thinned portions 14 comprise notches, for example. The thinnedportion 14 can have a semicircular shape. However, the shape of therespective thinned portion 14 is unimportant for the function thereof.The thinned portions 14 are formed at a top side and/or underside of therespective reinforcing element 13 a, 13 b. By way of example, thethinned portions 14 are stamped or milled in the top side and/or theunderside.

The thinned portions 14 can be open outward. For the respectivereinforcing element 13 a, 13 b this means that the thinned portion 14can be arranged at an outer side of the reinforcing element 13 a, 13 bwhich faces away from the top side 25 and respectively underside 26 ofthe actuator 11. The thinned portions 14 can also be open inward. Forthe respective reinforcing element 13 a, 13 b this means that thethinned portion 14 can be arranged at an outer side of the reinforcingelement 13 a, 13 b which faces toward the top side 25 and respectivelyunderside 26 of the actuator 11. The respective reinforcing element 13a, 13 b can have both inwardly and outwardly open thinned portions 14.The respective reinforcing element 13 a, 13 b can also have onlyone-sided thinned portions 14, that is to say thinned portions 14 whichare open either outward or inward.

The thinned portions 14 are provided to the effect that the reinforcingelement 13 a, 13 b can bend at the location of the thinned portion 14upon deflection of the actuator 11.

The thinned portions 14 are preferably formed in transition regions ofthe respective reinforcing element 13 a, 13 b. A thinned portion 14 isformed here in each case in the transition region between connectionregion 20 a, 20 b and end region 18 a, 18 b. These thinned portions 14are open inward in the exemplary embodiment according to FIGS. 2 to 4.Furthermore, a respective thinned portion 14 is found in the transitionregion between central region 19 a, 19 b and connection region 20 a, 20b. These thinned portions 14 are open outward in the exemplaryembodiment according to FIGS. 2 to 4.

In accordance with a further exemplary embodiment (FIG. 5), however, thethinned portions 14 can also be “turned over” in order to reduce thetotal height of the device 10. In this regard, in FIG. 5, the thinnedportions 14 in the transition region between connection region 20 a, 20b and end region 18 a, 18 b are open outward. The thinned portions 14 inthe transition region between central region 19 a, 19 b and connectionregion 20 a, 20 b are open inward. If the maximum height 6 of the freeregion 16 is set at only 1.16 mm, then the total height of the device 10from FIG. 5 is only less than or equal to 7.5 mm, preferably 7.36 mm.

In the transition regions the reinforcing element 13 a, 13 b must bendif the actuator 11 deforms. The thinned portions 14 ensure the necessaryflexibility of the reinforcing element 13 a, 13 b. As a result,transmission becomes movable for the actuator 11 and stiff for the load,for example, a touch-sensitive screen. The efficiency of thetransmission is increased as a result.

If voltage is then applied to the actuator 11, the partial regions 17 a,17 b of the respective reinforcing element 13 a, 13 b move relative tothe actuator 11 in a second direction R2 (FIGS. 2 and 3). The seconddirection R2 is perpendicular to the first direction R1. The seconddirection R2 extends along the stacking direction S.

In particular, the central regions 19 a, 19 b move in the direction R2.In this case, the respective reinforcing element 13 a, 13 b bends at thelocation of the thinned portions 14 between central region 19 a, 19 band connection regions 20 a, 20 b and also between connection regions 20a, 20 b and end regions 18 a, 18 b.

By contrast, a movement of the end regions 18 a, 18 b in the seconddirection R2 is prevented by the adhesive-bonding connection to theactuator 11. Rather, the end regions 18 a, 18 b move with the actuator11 in the first direction R1. As a result of the flexibility of thereinforcing elements 13 a, 13 b, the loading of the adhesive bonds hereis limited to less than or equal to 50 MPa. A relative movement betweenthe end regions 18 a, 18 b and the partial regions 17 a, 17 b thus takesplace. The haptic feedback of the device 10 is brought about by therelative movement of the respective end region 18 a, 18 b with respectto the respective partial region 17 a, 17 b.

If the device 10 is integrated as a drive for haptic feedback into anelectronic apparatus, then the reinforcing elements 13 a, 13 b arepreferably secured to mechanical elements (for example, a screen 40 anda weight 30). The mechanical elements 30, 40 are thus moved relative toone another upon a deformation of the piezoelectric actuator 11. Inother words, the screen 40 is offset laterally (parallel to the screensurface) and haptic feedback is produced as a result. This is shown inFIG. 6.

Displacements in the range of 100 μm to 150 μm are conceivable.Individual excursions (offset and return offset) are also possible. Anoffset is intended generally to have a duration of between 7 ms and 10ms. The lateral offset is employed since in the case of a verticaloffset (perpendicular to the surface), owing to the low flexuralstrength of the screen 40, the screen 40 would have to be driven at aplurality of locations. The use of a device 10 as described above issufficient in the case of a lateral offset.

The screens generally have a mass of between 300 g and 400 g. Screen 40and device 10 (drive) in a simplified depiction are an oscillatorymass-spring system. The resonant frequency f₀ (frequency of the freeoscillation without excitation) results as: f₀=½π·√(D/m). In this case,D is the stiffness of the drive 10 and m is the mass of the screen 40.f₀ must be greater than the reciprocal of the excursion duration T,otherwise the screen 40 does not move or only partly movesconcomitantly. It thus holds true that: D≥m(2π/T)². Given T=7 ms andm=400 g this results in a minimum stiffness of 0.32 N/μm for the device10 (drive).

For the above-described device 10 in accordance with FIGS. 2 to 5, givena voltage of 100 V, this results in a stroke of 117 μm, a blocking forceof 46 N and thus a stiffness of 0.4 N/μm.

To compare the performance capability of a transmission, it is possibleto use the maximum energy E_(max) able to be transmitted, for a givenactuator 11 with driving. E_(max)=(free travel·blocking force)/2. Thisvalue is 2.7 mJ for the device described above.

In the case where the thinned portions 14 according to embodiments ofthe invention are absent and with an assumed thickness of the respectivereinforcing element 13 a, 13 b of 0.5 mm and height h of 1.75 mm, adeflection of only 102 μm would be achieved, and a blocking force of 40N. This would result in a stiffness of 0.38 N/μm and Emax of 2.0 mJ.

The invention is not restricted by the description on the basis of theexemplary embodiments. Rather, the invention encompasses any novelfeature and also any combination of features, which in particularincludes any combination of features in the patent claims, even if thisfeature or this combination itself is not explicitly specified in thepatent claims or exemplary embodiments.

The invention claimed is:
 1. An assembly comprising: a screen with ascreen surface; and a device for producing haptic feedback, the devicecomprising: at least one piezoelectric actuator comprising a pluralityof piezoelectric layers; a first reinforcing element; and a secondreinforcing element, wherein the piezoelectric actuator is arrangedbetween the reinforcing elements, wherein the piezoelectric actuator isconfigured to alter its expansion in a first direction when anelectrical voltage is applied, wherein the first reinforcing element isconfigured to deform on account of an alteration in the expansion in thefirst direction of the piezoelectric actuator such that a central regionof the first reinforcing element is moved relative to the piezoelectricactuator in a second direction, the second direction being perpendicularto the first direction, wherein the second reinforcing element isconfigured to deform on account of the alteration in the expansion inthe first direction of the piezoelectric actuator such that a centralregion of the second reinforcing element is moved relative to thepiezoelectric actuator in a third direction, the third direction beingperpendicular to the first direction and opposite to the seconddirection, wherein the device is configured to bring about an offset ofthe screen parallel to the screen surface, wherein the assembly isconstructed such that D≥m(2π/T)² holds true, and wherein D is astiffness of the device, m is a mass of the screen, and T is anexcursion duration of the assembly.
 2. The assembly according to claim1, wherein the piezoelectric actuator is configured such that thealteration in the expansion in the first direction of the piezoelectricactuator takes place transversely with respect to a polarizationdirection of the piezoelectric layers and with respect to an electricfield such that the piezoelectric actuator is operated based on a d₃₁effect.
 3. The assembly according to claim 1, wherein the piezoelectricactuator comprises a top side and an underside, which are opposite toeach other in the second direction, wherein the first reinforcingelement comprises: a partial region including the central region, and atleast one end region directly adjacent to the partial region, whereinthe at least one end region of the first reinforcing element isconfigured such that upon the alteration in the expansion of thepiezoelectric actuator, a movement of the at least one end region in thesecond direction with respect to the top side of the piezoelectricactuator does not occur, wherein the second reinforcing elementcomprises: a partial region including the central region, and at leastone end region directly adjacent to the partial region, and wherein theat least one end region of the second reinforcing element is configuredsuch that upon the alteration in the expansion of the piezoelectricactuator, a movement of the at least one end region in the seconddirection with respect to the underside of the piezoelectric actuatordoes not occur.
 4. The assembly according to claim 3, wherein two endregions of the first reinforcing element are connected to the top sideof the piezoelectric actuator in a non-releasable manner, and whereintwo end regions of the second reinforcing element are connected to theunderside of the piezoelectric actuator in a non-releasable manner. 5.The assembly according to claim 3, wherein each end region abutsdirectly the piezoelectric actuator.
 6. The assembly according to claim3, wherein each end region and the piezoelectric actuator are connectedto one another by an adhesive connection.
 7. The assembly according toclaim 3, wherein each partial region is arranged at a distance from asurface of the piezoelectric actuator.
 8. The assembly according toclaim 3, wherein the first reinforcing element has two end regions and apartial region which is arranged between the two end regions, andwherein the second reinforcing element has two end regions and a partialregion which is arranged between the two end regions.
 9. The assemblyaccording to claim 1, wherein the first reinforcing element has at leastone thinned portion and is configured to bend at a location of thethinned portion upon a movement in the second direction, and wherein thesecond reinforcing element has at least one thinned portion and isconfigured to bend at a location of the thinned portion upon a movementin the third direction.
 10. The assembly according to claim 9, whereineach thinned portion has an indentation in a surface of the respectivereinforcing element.
 11. The assembly according to claim 9, wherein eachreinforcing element has a plurality of thinned portions.
 12. Theassembly according to claim 9, wherein each thinned portion is locatedin a transition region between the central region and an end region of arespective reinforcing element.
 13. The assembly according to claim 9,wherein a partial region of the first reinforcing element comprises thecentral region and at least one connection region, wherein the centralregion extends parallel to a surface of the piezoelectric actuator, andwherein a thinned portion is located in a transition region between thecentral region and the connection region of the first reinforcingelement, wherein a partial region of the second reinforcing elementcomprises the central region and at least one connection region, whereinthe central region extends parallel to the surface of the piezoelectricactuator, and wherein a thinned portion is located in a transitionregion between the central region and the connection region of thesecond reinforcing element.
 14. The assembly according to claim 1,wherein each reinforcing element is formed in integral fashion.
 15. Theassembly according to claim 1, wherein the haptic feedback is generatedby the offset of the screen parallel to the screen surface.